Methods of manufacturing microfabricated substrates

ABSTRACT

The present invention is directed to improved methods and apparatuses for manufacturing microfabricated devices, and particularly, microfluidic devices. In general the methods and apparatuses of the invention provide improved methods of bonding substrates together by applying a vacuum to the space between the substrates during the bonding process.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application is a continuation of U.S. patent applicationSer. No. 09/244,703, filed Feb. 4, 1999, which is a continuation-in-partof U.S. patent application Ser. No. 08/877,843, filed Jun. 18, 1997, nowU.S. Pat. No. 5,882,465, and incorporated herein by reference for allpurposes.

BACKGROUND OF THE INVENTION

[0002] Microfabricated devices are used in a wide variety of industries,ranging from the integrated circuits and microprocessors of theelectronics industry to, in more recent applications, microfluidicdevices and systems used in the pharmaceutical, chemical andbiotechnology industries.

[0003] Because of the extreme small scale of these devices, as well asthe highly precise nature of the operations which they perform, themanufacturing of these microfabricated devices requires extremely highlevels of precision in all aspects of fabrication, in order toaccurately and reliably produce the various microscale features of thedevices.

[0004] In a number of these disciplines, the manufacturing of thesemicrofabricated devices requires the layering or laminating of two ormore layers of substrates, in order to produce the ultimate device. Forexample, in microfluidic devices, the microfluidic elements of thedevice are typically produced by etching or otherwise fabricatingfeatures into the surface of a first substrate. A second substrate isthen laminated or bonded to the surface of the first to seal thesefeatures and provide the fluidic elements of the device, e.g., the fluidpassages, chambers and the like.

[0005] While a number of bonding techniques are routinely utilized inmating or laminating multiple substrates together, these methods allsuffer from a number of deficiencies. For example, silica-basedsubstrates are often bonded together using thermal bonding techniques.However, in these thermal bonding methods, substrate yields can often beextremely low, as a result of uneven mating or inadequate contactbetween the substrate layers prior to the thermal bonding process.Similarly, in bonding semi-malleable substrates, variations in thecontact between substrate layers, e.g., resulting from unevenapplication of pressure to the substrates, may adversely affect thedimensions of the features within the interior portion of the device,e.g., flattening channels of a microfluidic device, as well as theirintegrity.

[0006] Due to the cost of substrate material, and the more preciserequirements for microfabricated devices generally, and microfluidicdevices, specifically, it would generally be desirable to provide animproved method of manufacturing such devices to achieve improvedproduct yields, and enhanced manufacturing precision. The presentinvention meets these and a variety of other needs.

SUMMARY OF THE INVENTION

[0007] The present invention is generally directed to improved methodsof manufacturing microfabricated devices, and particularly, microfluidicdevices. In particular, in a first aspect, the present inventionprovides methods and apparatuses for bonding microfabricated substratestogether. In accordance with the methods of the present invention, afirst substrate is provided which has at least a first planar surface, asecond surface opposite the planar surface, and a plurality of aperturesdisposed through the first substrate from the first surface to thesecond surface. A vacuum is applied to the apertures, while the firstplanar surface of the first substrate is mated with a first planarsurface of the second substrate. The mating of these substrates iscarried out under conditions wherein the first surface of the firstsubstrate is bonded to the first surface of the second substrate. Suchconditions can include, e.g., heating the substrates, or applying anadhesive to one of the planar surfaces of the first or second substrate.

[0008] In a related aspect, the present invention also provides anapparatus for manufacturing microfluidic devices in accordance with themethods described above. Specifically, such apparatus typicallycomprises a platform surface for holding a first substrate, the firstsubstrate having at least a first planar surface and a plurality ofholes disposed therethrough, and wherein the platform surface comprisesa vacuum port connected to a vacuum source, for applying a vacuum to theplurality of holes. The apparatus also comprises a bonding system forbonding the first surface of the first substrate to a first surface of asecond substrate.

BRIEF DESCRIPTION OF THE FIGURES

[0009]FIG. 1 illustrates the layered fabrication of a typicalmicrofluidic device, from at least two separate substrates, whichsubstrates are mated together to define the microfluidic elements of thedevice.

[0010]FIG. 2 illustrates a mounting table and vacuum chuck for bondingsubstrates together according to the methods of the present invention.

[0011]FIG. 3 illustrates an apparatus for mounting and thermally bondingsubstrates together.

[0012]FIG. 4 illustrates a bonded substrate that includes multiplediscrete channel networks to be separated into individual microfluidicdevices.

DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention is generally directed to improved methodsof manufacturing microfabricated substrates, and particularly, toimproved methods of bonding together microfabricated substrates in themanufacture of microfluidic devices. These improved methods of bondingsubstrates are generally applicable to a number of microfabricationprocesses, and are particularly well suited to the manufacture ofmicrofluidic devices.

[0014] As used herein, the term “microscale” or “microfabricated”generally refers to structural elements or features of a device whichhave at least one fabricated dimension in the range of from about 0.1 μmto about 500 μm. Thus, a device referred to as being microfabricated ormicroscale will include at least one structural element or featurehaving such a dimension. When used to describe a fluidic element, suchas a passage, chamber or conduit, the terms “microscale,”“microfabricated” or “microfluidic” generally refer to one or more fluidpassages, chambers or conduits which have at least one internalcross-sectional dimension, e.g., depth, width, length, diameter, etc.,that is less than 500 μm, and typically between about 0.1 μm and about500 μm. In the devices of the present invention, the microscale channelsor chambers preferably have at least one cross-sectional dimensionbetween about 0.1 μm and 200 μm, more preferably between about 0.1 μmand 100 μm, and often between about 0.1 μm and 20 μm. Accordingly, themicrofluidic devices or systems prepared in accordance with the presentinvention typically include at least one microscale channel, usually atleast two intersecting microscale channels, and often, three or moreintersecting channels disposed within a single body structure. Channelintersections may exist in a number of formats, including crossintersections, “T” intersections, or any number of other structureswhereby two channels are in fluid communication.

[0015] The body structure of the microfluidic devices described hereintypically comprises an aggregation of two or more separate layers whichwhen appropriately mated or joined together, form the microfluidicdevice of the invention, e.g., containing the channels and/or chambersdescribed herein. Typically, the microfluidic devices described hereinwill comprise a top portion, a bottom portion, and an interior portion,wherein the interior portion substantially defines the channels andchambers of the device.

[0016]FIG. 1 illustrates a two layer body structure 10, for amicrofluidic device. In preferred aspects, the bottom portion of thedevice 12 comprises a solid substrate that is substantially planar instructure, and which has at least one substantially flat upper surface14. A variety of substrate materials may be employed as the bottomportion. Typically, because the devices are microfabricated, substratematerials will be selected based upon their compatibility with knownmicrofabrication techniques, e.g., photolithography, wet chemicaletching, laser ablation, air abrasion techniques, injection molding,embossing, and other techniques. The substrate materials are alsogenerally selected for their compatibility with the full range ofconditions to which the microfluidic devices may be exposed, includingextremes of pH, temperature, salt concentration, and application ofelectric fields. Accordingly, in some preferred aspects, the substratematerial may include materials normally associated with thesemiconductor industry in which such microfabrication techniques areregularly employed, including, e.g., silica based substrates, such asglass, quartz, silicon or polysilicon, as well as other substratematerials, such as gallium arsenide and the like. In the case ofsemiconductive materials, it will often be desirable to provide aninsulating coating or layer, e.g., silicon oxide, over the substratematerial, and particularly in those applications where electric fieldsare to be applied to the device or its contents.

[0017] In additional preferred aspects, the substrate materials willcomprise polymeric materials, e.g., plastics, such aspolymethylmethacrylate (PMMA), polycarbonate, polytetrafluoroethylene(TEFLON™), polyvinylchloride (PVC), polydimethylsiloxane (PDMS),polysulfone, and the like. Such polymeric substrates are readilymanufactured using available microfabrication techniques, as describedabove, or from microfabricated masters, using well known moldingtechniques, such as injection molding, embossing or stamping, or bypolymerizing the polymeric precursor material within the mold (See U.S.Pat. No. 5,512,131). Such polymeric substrate materials are preferredfor their ease of manufacture, low cost and disposability, as well astheir general inertness to most extreme reaction conditions. Again,these polymeric materials may include treated surfaces, e.g.,derivatized or coated surfaces, to enhance their utility in themicrofluidic system, e.g., provide enhanced fluid direction, e.g., asdescribed in U.S. Pat. No. 5,885,470, and which is incorporated hereinby reference in its entirety for all purposes.

[0018] The channels and/or chambers of the microfluidic devices aretypically fabricated into the upper surface of the bottom substrate orportion 12, as microscale grooves or indentations 16, using the abovedescribed microfabrication techniques. The top portion or substrate 18also comprises a first planar surface 20, and a second surface 22opposite the first planar surface 20. In the microfluidic devicesprepared in accordance with the methods described herein, the topportion also includes a plurality of apertures, holes or ports 24disposed therethrough, e.g., from the first planar surface 20 to thesecond surface 22 opposite the first planar surface.

[0019] The first planar surface 20 of the top substrate 18 is thenmated, e.g., placed into contact with, and bonded to the planar surface14 of the bottom substrate 12, covering and sealing the grooves and/orindentations 16 in the surface of the bottom substrate, to form thechannels and/or chambers (i.e., the interior portion) of the device atthe interface of these two components. The holes 24 in the top portionof the device are oriented such that they are in communication with atleast one of the channels and/or chambers formed in the interior portionof the device from the grooves or indentations in the bottom substrate.In the completed device, these holes function as reservoirs forfacilitating fluid or material introduction into the channels orchambers of the interior portion of the device, as well as providingports at which electrodes may be placed into contact with fluids withinthe device, allowing application of electric fields along the channelsof the device to control and direct fluid transport within the device.

[0020] Conditions under which substrates may be bonded together aregenerally widely understood, and such bonding of substrates is generallycarried out by any of a number of methods, which may vary depending uponthe nature of the substrate materials used. For example, thermal bondingof substrates may be applied to a number of substrate materials,including, e.g., glass or silica based substrates, as well as polymerbased substrates. Such thermal bonding typically comprises matingtogether the substrates that are to be bonded, under conditions ofelevated temperature and, in some cases, application of externalpressure. The precise temperatures and pressures will generally varydepending upon the nature of the substrate materials used.

[0021] For example, for silica-based substrate materials, i.e., glass(borosilicate glass, Pyrex™, soda lime glass, etc.), quartz, and thelike, thermal bonding of substrates is typically carried out attemperatures ranging from about 500° C. to about 1400° C., andpreferably, from about 500° C. to about 1200° C. For example, soda limeglass is typically bonded at temperatures around 550° C., whereasborosilicate glass typically is thermally bonded at or near 800° C.Quartz substrates, on the other hand, are typically thermally bonded attemperatures at or near 1200° C. These bonding temperatures aretypically achieved by placing the substrates to be bonded into hightemperature annealing ovens. These ovens are generally commerciallyavailable from, e.g., Fischer Scientific, Inc., and LabLine, Inc.

[0022] Polymeric substrates that are thermally bonded, on the otherhand, will typically utilize lower temperatures and/or pressures thansilica-based substrates, in order to prevent excessive melting of thesubstrates and/or distortion, e.g., flattening of the interior portionof the device, i.e., channels or chambers. Generally, such elevatedtemperatures for bonding polymeric substrates will vary from about 80°C. to about 200° C., depending upon the polymeric material used, andwill preferably be between about 90° C. and 150° C. Because of thesignificantly reduced temperatures required for bonding polymericsubstrates, such bonding may typically be carried out without the needfor high temperature ovens, as used in the bonding of silica-basedsubstrates. This allows incorporation of a heat source within a singleintegrated bonding system, as described in greater detail below.

[0023] Adhesives may also be used to bond substrates together accordingto well known methods, which typically comprise applying a layer ofadhesive between the substrates that are to be bonded and pressing themtogether until the adhesive sets. A variety of adhesives may be used inaccordance with these methods, including, e.g., UV curable adhesives,that are commercially available. Alternative methods may also be used tobond substrates together in accordance with the present invention,including e.g., acoustic or ultrasonic welding and/or solvent welding ofpolymeric parts.

[0024] Typically, a number of microfabricated devices will bemanufactured at a time. For example, polymeric substrates may be stampedor molded in large separable sheets which can be mated and bondedtogether. Individual devices or discrete channel networks may then beseparated from the larger bonded substrate sheet. Similarly, forsilica-based substrates, individual devices can be fabricated fromlarger substrate wafers or plates, allowing higher throughput of themanufacturing process. Specifically, a number of discrete channelnetworks, e.g., where each separate channel network includes at leasttwo intersecting channels, can be manufactured into a first substratewafer or plate. A second wafer or plate is then provided that includes aplurality of holes disposed through it, which holes align with theunintersected termini of the various channel networks. The two substratewafers are first bonded together such that multiple channel networks arecreated in the integrated substrate. The resulting multiple devices arethen segmented from the larger substrates using known methods, such assawing (See, e.g., U.S. Pat. No. 4,016,855 to Mimata, incorporatedherein by reference), scribing and breaking (See Published PCTApplication No. WO 95/33846), and the like. In particular, a largebonded substrate including multiple separate and discrete channelnetworks is separated into individual devices by, e.g., sawing themapart, scribing between the channel networks and breaking them apart. Inthe case of polymeric substrates these methods are also as applicable,however, discrete devices may be cut or melted apart. In some cases,where the fabrication process has included perforations or thinner areasof the bonded substrates, the discrete devices may be simply snapped orbroken apart. An example of this fabrication method is schematicallyillustrated in FIG. 5. As shown, the bonded substrate (seen only fromabove) includes the apertures 24 as described with reference to FIG. 1.These apertures are in fluid communication with discrete channelnetworks (not shown) in the interior portion of the bonded substrate 50.The discrete channel networks or individual microfluidic devices arethen separated from the larger sheet along, e.g., dashed lines 52.Depending upon the method employed, these dashed lines may be the linesalong which sawing or scribing and breaking take place, or they caninclude perforated regions or thinned substrate regions which may beeasily broken apart.

[0025] Typically, these larger wafer techniques may be used tosimultaneously fabricate at least 4 separate microfluidic devices, e.g.,as discrete channel networks in the larger wafer, typically at least 8separate devices, preferably at least than 10 separate devices, morepreferably at least 20 separate devices and still more preferably, atleast 40 separate devices from a single bonded substrate.

[0026] As noted above, the top or second substrate is overlaid upon thebottom or first substrate to seal the various channels and chambers. Incarrying out the bonding process according to the methods of the presentinvention, the mating of the first and second substrates is carried outusing vacuum to maintain the two substrate surfaces in optimal contact.In particular, the bottom substrate may be maintained in optimal contactwith the top substrate by mating the planar surface of the bottomsubstrate with the planar surface of the top substrate, and applying avacuum through the holes that are disposed through the top substrate.Typically, application of a vacuum to the holes in the top substrate iscarried out by placing the top substrate on a vacuum chuck, whichtypically comprises a mounting table or surface, having an integratedvacuum source. In the case of silica-based substrates, the matedsubstrates are subjected to elevated temperatures, e.g., in the range offrom about 100IC to about 200° C., in order to create an initial bond,so that the mated substrates may then be transferred to the annealingoven, without any shifting relative to each other.

[0027] One example of an apparatus for use in accordance with themethods described herein is shown in FIG. 2. As shown, the apparatusincludes a mounting table 30, which comprises a platform surface 32,having a vacuum port 34 disposed therethrough. In operation, the topsubstrate, e.g., having the plurality of holes disposed therethrough, isplaced upon the platform surface and maintained in contact with thatsurface by virtue of the application of a vacuum through vacuum port 34.Although FIG. 2 shows the platform surface as being the upper surface ofthe mounting table, it will be appreciated that such a device would alsofunction in an inverted orientation, relying upon the applied vacuum tomaintain the substrate in contact with the platform surface. Theplatform may also comprise one or more alignment structures formaintaining the substrate in a set, predefined position. These alignmentstructures may take a variety of forms, including, e.g., alignment pins36, alignment ridges, walls, or wells disposed upon the mountingsurface, whereupon placement of the substrates in accordance with suchstructures ensures alignment of the substrates in the appropriateposition, e.g., over the vacuum port, as well as aligning the individualsubstrate portions with other substrate portions, as described ingreater detail below. In addition to such structures, alignment may alsobe facilitated by providing the platform at an appropriate angle, suchthat gravity will maintain the substrate in contact with the alignmentstructures. Vacuum port 34 is disposed through the platform surface andmounting table, and is connected via a vacuum line 38 to a vacuum source(not shown), e.g., a vacuum pump.

[0028] The first substrate is placed upon the platform surface such thatthe planar surface of the top substrate faces away from the platformsurface of the mounting table, and such that the holes in the substrateare in communication with the vacuum port in the platform surface of themounting table. Alignment of the holes over the vacuum port is typicallyaccomplished through the incorporation of alignment structure orstructures upon the mounting table platform surface, as described above.In order to apply vacuum simultaneously at a plurality of the holes inthe top substrate, a series of vacuum ports may be provided through theplatform surface. Preferably, however, the platform surface comprises aseries of grooves 40 fabricated therein, and extending outward from asingle vacuum port, such that each of the plurality of holes in the topsubstrate will be in communication with the vacuum port via at least oneof these grooves or “vacuum passages,” when the top substrate is placedupon the platform surface.

[0029] The bottom substrate, also having a first planar surface, is thenplaced on the top substrate such that the first planar surface of thebottom substrate mates with that of the top substrate. Again, thealignment structures present upon the platform surface will typicallyoperate to align the bottom substrate with the top substrate as well asmaintain the substrates over the vacuum port(s). The alignment of thevarious substrate portions relative to each other is particularlyimportant in the manufacture of microfluidic devices, wherein eachsubstrate portion may include microfabricated elements which must be influid communication with other microfabricated elements on anothersubstrate portion.

[0030] A vacuum is then applied through the vacuum passages on theplatform surface, and to the holes through the top substrate. This actsto pull the two substrates together by evacuating the air between theirplanar surfaces. This method is particularly useful where the top andbottom substrates are elements of microfluidic devices, as describedabove. Specifically, upon mating the top substrate with the bottomsubstrate, the holes disposed through the top substrate will generallybe in communication with the intersecting channel structures fabricatedinto the planar surface of the bottom substrate. In these methods, thechannel networks enhance the efficiency of the bonding process. Forexample, these channel networks typically cover large areas of thesurface of the bottom substrate, or the space between the twosubstrates. As such, they can enhance the efficiency with which air isevacuated from this space between the two substrates, ensuringsufficient contact between the substrates over most of the planarsurfaces of the two substrates for bonding. This is particularly thecase for those areas between the substrates that are immediatelyadjacent the channel structures, where complete bonding is morecritical, in order to properly seal these channels.

[0031] In addition to more efficiently removing air from between thesubstrates, the application of vacuum at each of the plurality of holesin the top substrate, as well as through the intersecting channelstructures between the two substrates results in a more even applicationof the pressure forcing the substrates together. Specifically, unevenlyapplied pressures in bonding methods can have substantial adverseeffects on the bonding process. For example, uneven application ofpressures on the two substrates during the bonding process can result inuneven contact between the two surfaces of the two substrates, which, asdescribed above, can reduce the efficiency and quality, as well as theeffective product yield of the bonding process.

[0032] Further, even where substrates are completely bonded under suchuneven pressure, e.g., for thermally bonded polymeric substrates orsubstrates bonded with adhesives, such uneven pressures can result invariations in the dimensions of the internal structures of the devicefrom one location in a microfabricated device to another. Again, thechannel networks extending across wide areas of the interior portion ofthe two substrates, e.g., fabricated into the surface of the secondsubstrate, allows application of vacuum across a substantially larger,and more evenly distributed area of the substrates interior portion.

[0033] In addition to the vacuum chuck, the bonding system shown in FIG.3 also includes a heat source, e.g., a controllable heat source such asheat gun 42, for elevating the temperature of the substrates 12 and 18while they are mounted on the platform surface/mounting table 30. Forbonding silica based substrates, this heat source applies an elevatedtemperature to the two substrates to create a preliminary bond betweenthe substrates, so that they can be readily transferred to an annealingoven without the substrates shifting substantially relative to eachother. This is generally accomplished by heating the two substrates tobetween about 90° C. and about 200° C. In the case of polymericsubstrates, this heat source can take the place of the annealing oven byelevating the temperature of the polymeric substrates to appropriatebonding temperatures, e.g., between about 80° C. and 200° C. Further,this can be done while the substrates are mounted upon the mountingtable, and while a vacuum is being applied to the substrates. This hasthe effect of maintaining an even, constant pressure on the substratesthroughout the bonding process. Following such initial bonding, thesubstrates are transferred to an annealing oven, e.g., as describedabove, where they are subjected to bonding temperatures between about500° C. and 1400° C., again, as described above.

[0034] Although illustrated in FIG. 3 as a heat gun, it will be readilyappreciated that the heat source portion of the apparatus may includemultiple heat sources, i.e., heat guns, or may include heating elementsintegrated into the apparatus itself. For example, a thermoelectricheater may be fabricated into or placed in thermal contact with theplatform surface/mounting table 30, which itself, may be fabricated froma thermally conductive material. Such thermal bonding systems areequally applicable to both polymeric substrates and silica basedsubstrates, e.g., for overall bonding of polymeric substrates, or forproducing the initial, preliminary bonding of the silica-basedsubstrates.

[0035] Alternate bonding systems for incorporation with the apparatusdescribed herein include, e.g., adhesive dispensing systems, forapplying adhesive layers between the two planar surfaces of thesubstrates. This may be done by applying the adhesive layer prior tomating the substrates, or by placing an amount of the adhesive at oneedge of the adjoining substrates, and allowing the wicking action of thetwo mated substrates to draw the adhesive across the space between thetwo substrates.

[0036] In certain embodiments, the overall bonding system can includeautomatable systems for placing the top and bottom substrates on themounting surface and aligning them for subsequent bonding. Typically,such systems include translation systems for moving either the mountingsurface or one or more of the top and bottom substrates relative to eachother. For example, robotic systems may be used to lift, translate andplace each of the top and bottom substrates upon the mounting table, andwithin the alignment structures, in turn. Following the bonding process,such systems also can remove the finished product from the mountingsurface and transfer these mated substrates to a subsequent operation,e.g., separation operation, annealing oven for silica-based substrates,etc., prior to placing additional substrates thereon for bonding.

[0037] Although the present invention has been described in some detailby way of illustration and example for purposes of clarity andunderstanding, it will be apparent that certain changes andmodifications may be practiced within the scope of the appended claims.All publications, patents and patent applications referenced herein arehereby incorporated by reference in their entirety for all purposes asif each such publication, patent or patent application had beenindividually indicated to be incorporated by reference.

What is claimed is:
 1. A method of fabricating microfluidic devicescomprising: providing a first substrate and a second substrate, whereinthe second substrate has a plurality of apertures; applying a vacuum tothe apertures to hold the first substrate in contact with the secondsubstrate; and bonding the first substrate to the second substrate. 2.The method of claim 1, wherein the bonding step comprises heating thefirst and second substrates to bond a first surface of the firstsubstrate to a first surface of the second substrate.
 3. The method ofclaim 2, wherein the step of heating the substrates comprises heatingthe first and second substrates to a temperature between about 80° C.and 200° C.
 4. The method of claim 3, wherein the first and secondsubstrates comprise polymeric substrates.
 5. The method of claim 2,wherein the first and second substrates comprise silica-basedsubstrates, and wherein the bonding step comprises heating the first andsecond substrates to between about 90 and 200° C., followed by the stepof heating the first and second substrates to a temperature betweenabout 500° C. and 1400° C.
 6. The method of claim 1, wherein the bondingstep comprises applying an adhesive to at least one of a first surfaceof the first substrate or a first surface of the second substrate priorto applying a vacuum to the apertures of the second substrate.
 7. Themethod of claim 1, wherein the first and second substrates compriseglass.
 8. The method of claim 1, wherein the first and second substratesare comprised of polymeric materials.
 9. The method of claim 1, whereinthe first substrate includes a plurality of discrete microscale channelnetworks disposed on a first surface of the first substrate.
 10. Themethod of claim 9, wherein the first substrate includes at least fourdiscrete microscale channel networks disposed on the first surface ofthe first substrate.
 11. The method of claim 9 wherein the firstsubstrate includes at least ten discrete microscale channel networksdisposed on the first surface of the first substrate.
 12. The method ofclaim 9 wherein the first and second bonded substrates form a unitarybonded substrate, the method further comprising separating a firstportion of the bonded substrate containing at least a first discretechannel network from a second portion of the bonded substrate containingat least a second discrete channel network.
 13. The method of claim 12,wherein the bonded substrate comprises a thinned region between at leastthe first and second discrete channel networks, and the separating stepcomprises breaking the first discrete channel network from at least thesecond discrete channel network along the thinned region.
 14. The methodof claim 12, wherein the bonded substrate comprises a perforated regionbetween at least the first and second discrete channel networks, and theseparating step comprises breaking the first discrete channel networkfrom at least the second discrete channel network along the perforatedregion.
 15. The method of claim 9 wherein the plurality of apertures arepositioned in fluidic communication with the plurality of discretemicroscale channel networks prior to said bonding step.
 16. The methodof claim 1 further comprising aligning the first substrate with thesecond substrate prior to said applying vacuum.
 17. The method of claim1 wherein said applying vacuum is performed by placing the secondsubstrate upon a platform surface which includes a plurality of groovesfabricated therein which extend laterally from one or more vacuum portsin the platform surface, and applying a vacuum to the one or more vacuumports.
 18. The method of claim 1 wherein said applying vacuum isperformed by placing the second substrate upon a platform surface whichincludes a plurality of vacuum ports fabricated therein, and applying avacuum to the plurality of vacuum ports.